1. Field of the Invention
The invention relates to a process for the preparation of tert-(cyclo ) alkyl 1-hydrogen-2-hydrocarbylcyclopropanecarboxylates or 1-tert-(cyclo)alkyl (cyclo)alkyl spiro[2,p]alkanecarboxylates, p representing an integer of at least 2.
2. Description of the Prior Art
2,2-Dihalocyclopropanecarboxylates and certain derivatives thereof - as stated in the Netherlands Pat. application Nos. 7,205,298 and 7,212,973 - are biologically active, exhibiting in particular fungicidal and pesticidal properties. The fungicidal activity is especially marked against rice blast (Pyricularia oryzae). The pesticidal activity is shown by certain of the compounds against a wide range of insect and acarid pests.
Certain 2,2,3,3-tetraalkylcyclopropanecarboxylates - as stated in British Pat. specification No. 1,243,858, are also biologically active, combining a high insecticidal activity with low mammalian toxicity.
2,2-Dihalocyclopropanecarboxylic acids, from which the above-mentioned 2,2-dihalocyclopropanecarboxylates are derived, may easily be prepared from simple precursors. This can be explained as follows for the preparation of 2,2-dichloro-3,3-dimethylcyclopropanecarboxylic acid. 2-Methyl-2-pentene-4-one (mesityl oxide) is converted by means of the haloform reaction into potassium 3-methylcrotonate, which in turn is converted into the corresponding tert-butyl ester. Then, dichloromethylene generated in situ is added to this ester according to Netherlands patent application 7306662 to form tert-butyl 2,2-dichloro-3,3-dimethylcyclopropanecarboxylate, from which the corresponding acid can be prepared.
The 2,2,3,3-tetraalkylcyclopropanecarboxylic acid from which the above-mentioned 2,2,3,3-tetraalkylcyclopropanecarboxylates are derived can be prepared by (a) reaction of alkenes with a diazoacetic ester in the presence of a cupric sulphate catalyst, as described in Chemical Abstracts 54,24436 d, followed by liberation of the acid from the ester obtained, or (b) base-induced skeletal rearrangement of alpha-halogenated cyclobutanones, as described by J. M. Conia in Accounts of Chemical Research 5 (1972) 40, or (c) addition of a Grignard reagent to the double bond of cyclopropene hydrocarbons, as described in Chemical Abstracts 72, 132113 K, followed by reaction of the addition compound with dry ice and acidification.
The above shows that the 2,2,3,3-tetramethylcyclopropanecarboxylates are considerably more difficult to prepare than the 2,2-dihalocyclopropanecarboxylates. It would therefore be very attractive if there were a process for the replacement of the two halogen atoms in the 2,2-di-halocyclopropanecarboxylates by two alkyl groups. The present invention provides such a process.